Adjustment of the carding machine elements to thermal expansion effects

ABSTRACT

The invention relates to elements for a carding machine, which maintain the desired surface shape during a specific production following a possible warm-up phase when producing card slivers while ensuring the same distance between the roller fittings and the opposite element across the entire operating width of the roller.

The invention relates to elements for a card, which, after a possible warming up period during the production of card webs for a certain type of production, receive the desired surface form, which guarantees the same distance between the clothing of the roller and the counter element across the work width of the roller.

Trimmed rollers are used in many places within spinning frames. These rollers mostly comprise at least two roller shields or flanges at the front surface, in which shield or flange on the one hand the roller is rotatable mounted and which, on the other hand, can comprise bearing elements for mounting and/or supporting additional work elements. The work elements have in common that they are somewhat longer than the working width of the roller, and that they rest on the bearing elements on the left and on the right, for example segment curves, cover segments or (flexible-) curves, some of which are partially also adjustable.

These work elements can be divided into two main groups: stationary work elements which are arranged stationary, for example carding elements, casing elements, knives, grids, or guide elements, and work elements that are moved which are pulled by means of an endlessly rotating tape, for example by means of a chain or a belt, across the bearing surface of the bearing elements, for example the flat of a card.

Rollers in spinning frames, in particular in blow room machines, for example in cleaners or in cards, are, besides being surrounded by casing segments, also surrounded by knives, grids, carding segments or guide elements. These can have the form of plates or rods, and can possibly be furnished with clothing e.g. saw tooth clothing and they always have a side which is arranged opposite the clothing of the roller. The distance between this side and the clothing of the roller is adjusted as precisely as possible. This setting affects, depending on the function of the element, amongst other things the carding quality and/or the amount of dirt separation. Particularly with the carding segments a short distance increases the carding quality of the card and reduces the number of neps in the card web. An optimal setting is then achieved when the desired distance is equal across the entire work width during operation. Since these settings lie within the range of tenths of millimetres, deviations of already one hundredth of a millimetre can have a substantial effect on the function of the individual segments. In addition, due to the homogeneous load application on the elements across the entire work width, the wear duration is prolonged.

However this desired fine-tuning across the entire width of the card is difficult to achieve. The thermal expansion and its effect on the different elements of the card are explained in more detail in the following.

During start-up of the operation of the card, i.e. with the beginning of the production of a card web, the card undergoes a warm-up period. The duration of the warming-up period and the generated warming-up level is influenced by the drum speed, by the production rate and by the selected settings of the elements to each other. At lower and at higher production rate, the warming up time is more or less the same; the generated heat is, however, higher at a high production rate. During this warming-up period the various components expand due to the warming up. With a high performance card operation is at a high production rate, which leads to an additional temperature increase. Above all, tight settings between carding element, flats or knives, and drum represent a danger, because the elements can touch one another. For example: a desired carding gap between a carding element, made from an aluminium profile, and the drum amounts to 0.5 mm at a cold setting—that is, before starting the operation of the card. With a production rate of 150 kg/h, the effective gap is only 0.2 mm wide after the preheating time of the card. This decrease of 0.3 mm is caused by the thermal expansion of the drum surface and the carding surface and the thermal expansion of the work elements, as well as by the fibre/metal friction which occurs between the carding elements during the card web production.

From WO 79/00983 a technique is known for checking the operating conditions in a card with two rotating drums. Among other things, the distance between the two drums is changed for the compensation of the warming-up. This change takes place by means of cylinders, which are lengthwise variable in such a manner that they can change the distance of the axis of the drums in dependence of the momentary temperature. In another exemplified embodiment also a card with a drum and a revolving flat aggregate is illustrated in place of two drums. In this exemplified embodiment (FIG. 3) the distance between the revolving flat aggregate and the axes of the drum is changed with a cylinder. The recording of the respective temperature at the drum takes place with a sensor, by means of which the change of the cylinder is initiated through a control unit. A disadvantage of this device are the high requirements needed in order to control the system. Sensors as well as control devices and setting elements are required which must be coordinated, in order to effect, in dependence of previously defined conditions, a change of the distance between the drum and the revolving flat aggregate and/or the distance between the two drums. A failure of the control elements causes a wrong production, since the distance between the drum and the revolving flat aggregate does not exist any longer in the required length and the fibres are no longer carded with the required accuracy.

From EP 0 071 166 A 1 devices for the cooling of the drum of a card are known. According to the disclosure of this patent application it is attempted to keep the drum at a certain surface temperature by means of liquid containing channels which are arranged within the drum. Thus it should be achieved that the temperature of the cylinder is kept essentially constant during operation of the card and that thus the expansion of the drum with regard to a revolving flat aggregate is kept low or is avoided. The disadvantage of such a layout is, that it is very hard to introduce liquid into the inside of the drum. For this a hollow shaft is required in order to feed the liquid into the inside of the drum and to remove it again therefrom. In addition the temperature of the liquid and/or the drum has to be monitored, in order to be able to react to the respective operating temperature. The illustrated solution of the problem is thus likewise very cost-intensive in its production as well as in its maintenance. From EP 0 431 485 B1 and EP 1 031 650 cards are known, where also a solution of the heat removal is looked for.

The above-mentioned solutions have the disadvantage that they offer either only a solution across the entire width or only ease the heat effects, as this is the case with the cooling.

By the warming-up, however, not only a thermal expansion over the entire working width of the card results, but also heat gradients results across the shapes of the various components of the card. For example on the drum surface a temperature of 45° C. can result. A rigid type of segment arranged at the drum will also reach approximately this temperature on the side of the drum clothing. Contrary, on the side of the carding segment turned away from the drum, which has, due to the design (due to the work width and the accuracy of the elements), backs that are several centimetres high, the temperature reaches a clearly lower value (e.g. 28° C.). The difference in temperature across a rigid card segment can thus amount to some degrees Celsius. The size of this temperature difference depends on the condition of the segment (construction, material), the performed carding work (speed, production rate), the distance between the element and the roller, and the way the heat, which develops, is removed. In EP 1 031 650 an example is given for a card design, which removes the developing heat in a better way.

This heat gradient causes a bending of the elements across the width of the card. Due to this deflection a closer carding gap results at the centre than at the outer zone. Thereby an uneven carding gap results, which becomes wider in outward direction. This leads to a reduced carding quality and/or insufficient dirt separation and/or or insufficient nep dissolving. Likewise this can lead to “sideward flight” of the fibres. That means, that fibres collect in the edge regions, and/or even get deposited outside the work-width.

These effects appear rather rarely in a commercially normal card with a work width of 1 meter. With the new generation of high performance cards the work width is, however, larger than 1 meter, for example 1.5 meters. The deviation, which results from the above-mentioned effects, cannot be neglected here, but poses a problem for the entire carding quality of the card.

The invention is based on the task to create a card element of the above described kind which avoids the disadvantages mentioned, which in particular designs the elements of the card in such a way, that the heat effects after the warming-up period are eliminated and that constant carding gaps are achieved at a given production rate.

The solution of this task is given with the characteristic features of claim 1. In that the elements across the work width of the card are designed as hollow profiles, after the warming-up phase a profile form is achieved due to the temperature influence, at a predetermined production rate, which corresponds with a straight manufactured profile. The elements, which are suitable for this, are in particular the rollers, the flats of the revolving flat cards and the stationary work elements, for example knives, carding segments or guide elements.

The solution according to the invention is applicable in principle on all card elements, which comprise a surface, which are or come in contact with fibre material. These are both the work elements, for example carding segments, knives, tongue or flats, as well as all rollers, for example drum roller, doffer roller, licker-in rollers.

With the term “hollow” is meant that the element, on the side where it comes into contact with the fibre material, is formed concave at least in one dimension of the element, across the work width of the card, or in other words, the element has a concave arch shape across the work width of the card.

An example would be a hollow profile at a production rate of 60 kg/h and a drum speed of 850 min-1. This production rate is very often used for fibre tapes intended to produce high-quality threads, (e.g. combed ring spinning threads). The hollow profile, in cold condition, has a maximum difference between the centre of the element and the end face of the element of for example 0.2 mm or expressed in other words: the profile was manufactured with a 0,2 mm hollow shape. After the warming-up phase the element is thermally stable or expressed in other words, in a stationary thermal condition. By means of the different warming-up effects this thermal stabilization has led to the fact that the element again is formed as a straight line. The hollow profile is laid out in such a manner across the work width that the heat effect becomes balanced, preferably with the production of high-quality threads.

Preferably all rollers and work elements are designed hollow-shaped in such a manner that, after the warming-up phase (when the stationary thermal condition of the card is achieved), they form a straight surface. In particular the drum and the assigned work elements are most suitable for this design according to the invention. At the drum the closest settings are selected at the card. Due to the close settings and the high circumferential speed of the drum (the highest at the card) the fibre/metal friction between drum and work elements is the highest there which leads to the highest warming-up level on the card. Thus the distances between the elements and the card are influenced the most there. The smaller this distance and the more precisely it is adjusted and that it can be kept across the work width of the card, the higher is the quality of the produced card web and/or the final product (e.g. thread).

Since elements such as rollers or work elements have different expansion forms and thus different thermal expansions, the correction should be laid-out for an ideal production rate; particularly the card can be designed altogether for an ideal production rate. In particular the expansions to be expected should be considered in such a way, that no collision is possible between them and that, in particular, no resetting of the distance between the individual elements is necessary. A card according to the described invention has individually formed hollow elements in such a manner that the correction of all elements results in an even work gap. The invention is, however, not only limited to a card as such, it can in particular also be applied for individual structural units/groups.

In the following the invention is explained in more detail by way of the figures. For all drawings the same reference numerals are used, wherein is shown,

FIG. 1 a schematic side view of a card;

FIG. 2A to 2E a schematic illustration of the heat effects and the solutions according to the invention, across the work width of the card.

FIG. 1 shows a revolving flat card, e.g. the Rieter card C60 with a working width of 1.5 meters, with a filling chute 1. Fibre flakes are transported through the different cleaning process stages by way of transportation channels (not shown) and are finally supplied to the filling chute of the card. This then supplies the fibre flakes, in the form of cotton wool, further on to the card. The feed roller 3 and feeding trough 4 together feed the fibre flakes to the taker-in 5 a, 5 b and 5 c. The taker-in opens the fibre flakes and removes part of the dirt particles. The final taker-in roller 5 c transfers the fibre to the card drum 6. The card drum 6 co-operates with the flats 7 and thereby still further parallelizes the fibres. After the fibres have partially run several circulations on the card drum 6, they are taken off from the card drum 6 by the receiver roller 8, supplied to the squeezing roller 9 and finally deposited in a can (not shown) as lap 10.

Stationary work elements can in principle be arranged to any roller of the card. In particular the taker-in 5 a, 5 b and 5 c and the drum 6 are very often furnished with cleaning components such as knives 18, or carding elements 17. The accurate number of work elements and their arrangement can vary from card to card. Basically, however, most rollers are completely covered so that no fibres, dirt and dust can exit. At the transfer point from roller to roller one finds rather guiding elements or a tongue. But also at the rollers within the filling chute stationary work elements can be arranged, for example the EP 787841 discloses cleaning components which are assigned to the dissolving part.

The drum 6 can be divided into four subsections. The pre-carding zone 12, the main carding zone 13, the re-carding zone 14 and the sub-carding zone 15. In a revolving flat card the revolving flat 11 forms the main carding zone 13, while the pre-carding zone, the re-carding zone and the sub-carding zone are mostly equipped with stationary work elements. There are, however, also cards, which do not have a revolving flat, instead there are then stationary work elements within the main carding zone. These stationary work elements can consist of covering elements or casing elements 16, carding elements 17, knives, possibly with a suction device 18, or guide elements 19.

FIGS. 2A to 2E schematically illustrate the problem of the thermal expansion and the outline of the solution according to the invention. As an example a combination of a stationary work element 20 and a roller 21 was selected. Furthermore, the solution according to the invention can, however, also be applied in other combinations e.g. two rollers or a flat rod opposite a roller.

In FIG. 2A the work gap 22 is shown as even across the entire work width. The stationary operating condition is the desired situation. In order to avoid a collision between the two elements, in practice this work gap is very often adjusted somewhat wider in a cold card. After the card has reached its stationary thermal condition, the work gap is reset to the desired measurement.

FIG. 2B shows the situation after the temperature increase of the card elements, whereby, due to the thermal expansion, the surface of the elements are bomb-shaped (or bellied). The largest expansion effects are in the centre of the work width, indicated with the numeral 23 in the drawing. Thereby the work gap is substantially narrower here than in the edge zones.

FIG. 2 c shows, in addition to these heating effects, also the temperature differences across the extent from the outer side and to the centre 24. This can, depending on the condition and the position of the elements, run both in the direction of the work width as shown at the roller or radially as shown in the work element. With work elements such as flat rods or stationary work elements for example, this can lead to a bending of the entire element.

An outline of a solution according to the invention is shown in FIG. 2D. The work side is finished or otherwise adjusted to achieve a sufficiently hollow shape so that, after the warming-up phase, the carding gap takes on an even shape across the entire work width. The measurement of the hollow finishing 25 corresponds with the expected heat expansion with the desired production rate. Preferably, elements positioned opposite each other are corrected in such a manner that they, after the thermal expansion, together reach the desired work gap, without the need of a reset.

FIG. 2E shows a further embodiment according to the invention. In this embodiment only one of the two elements is corrected, in the drawing e.g. the work element, while the roller opposite is not corrected. After the heat stabilization thereby a work gap results, which is constant across the entire work width, although the shape of the gap is not straight, as is described in FIG. 2A. This outline of a solution has the advantage that only a part of the card elements need to be adapted.

The elements can either be worked/finished only on the work surface, or the element is adjusted as a whole object. The finishing can take place during the production of the elements and/or during re-finishing. As working procedures for example, lathing, bending, milling or grinding are suitable. In general the correction is larger than the manufacturing tolerance, which normally is to be maintained during the production of carding elements.

The solution according to the invention is independent of the choice of material of the individual elements applicable. 

1. Element for a card which, at least with one of its sides, can come into contact with the fibre material, characterized in that the element at this side comprises a concave curve across the work width of the card. 2-7. (canceled) 